Abstract P2-08-01: Licochalcone A from licorice reprograms metabolic and antioxidant pathways in the breast leading to a tumor preventive environment
Authors: Atieh Hajirahimkhan, Elizabeth T. Bartom, Sriram Chandrasekaran, Susan Clare, Seema Khan
Journal: Cancer Research (2023)

Abstract Background: Increased adiposity is a risk factor for postmenopausal breast cancer. It is often accompanied by chronic low-grade inflammation and elevated levels of reactive oxygen species, which drive breast tumorigenesis. Risk reducing drugs such as selective estrogen receptor modulators and aromatase inhibitors, which have demonstrated efficacy, have had a significantly low acceptance among women at high risk for breast cancer. This hesitancy is mainly due to the adverse side effects of these medications such as vasomotor symptoms, osteoporosis, thromboembolism, and uterine cancer. Therefore, alternative strategies with lower toxicity and greater acceptability are needed. We have previously shown that licochalcone A (LicA) from licorice (Glycyrrhiza inflata), which has osteogenic effects, suppresses aromatase expression and activity, enhances the activity of detoxifying enzymes, and reduces estrogen genotoxic metabolism in cell lines and animal models. However, its effects on the breast tissue of high-risk women are understudied. We hypothesize that LicA creates a tumor preventive environment in the breast by locally modulating adipogenesis and antioxidant/anti-inflammatory responses leading to decreased proliferation. Methods: We prepared microstructures from fresh tissue of contralateral unaffected mastectomy specimens of 6 postmenopausal women with incident unilateral breast cancer. We exposed these to DMSO (control) and LicA (5 µM) for 24 h. Employing total RNA sequencing, we examined differential gene expression between treated and control samples. Up-regulated and down-regulated genes were analyzed using Enrichr gene ontology (GO) pathway analysis. Enriched pathways with combined enrichment scores &amp;gt; 4 and FDR &amp;lt; 0.05 were considered statistically significant. Metabolism flux analysis was performed (FDR &amp;lt; 0.05). Live cell imaging to monitor proliferation of pre-malignant DCIS.COM, DCIS.COM/ER+ PR+; and malignant MDA-MB-231 (ER- PR-), MCF-7 (ER+ PR+), MCF-7aro, and BRCA1 defective HCC-1937, and HCC3153 cells was conducted using IncuCyte. Single versus repeated dosing of various concentrations of LicA were also evaluated. Results: We observed significant (P &amp;lt; 0.05) upregulation up to 8-fold of antioxidant genes, consistent with significant upregulation of NRF2, the major regulator of antioxidant pathways. This was accompanied by significant (P &amp;lt; 0.05) downregulation of NF-kB dependent inflammatory pathways. In addition, we observed the significant (P &amp;lt; 0.05) downregulation, ranging from 4 to 32-fold of cholesterol biosynthesis and transport, steroid hormone biosynthesis, as well as lipid metabolism genes, consistent with the profound downregulation of SREBF1 and SREBF2, which encode the master regulator of adipogenesis, SREBP. Metabolic flux results demonstrated a robust increase (FDR &amp;lt; 0.05) in the pentose phosphate shunt and NAD(P)H generation without enhancing ribose 5 phosphate formation, confirming an antioxidant and anti-proliferative environment. Likewise, LicA suppressed proliferation of pre-malignant and malignant cells dose- and time-dependently. Repeated dosing of lower concentrations of LicA (&amp;lt; 10 µM) demonstrated sustained antiproliferative effects even in the aggressive cancer cell lines. Conclusion: Our data suggest that LicA can generate a tumor-preventive breast microenvironment by reprogramming metabolic pathways involved in steroid and lipid homeostasis and antioxidant responses. These observations along with its low toxicity, suggest that LicA is a good candidate for further investigation as a breast cancer prevention agent. Citation Format: Atieh Hajirahimkhan, Elizabeth T. Bartom, Sriram Chandrasekaran, Susan Clare, Seema Khan. Licochalcone A from licorice reprograms metabolic and antioxidant pathways in the breast leading to a tumor preventive environment. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-08-01.